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Discussion Starter · #1 ·
Its almost 10 days that i have installed vance and hines high exhaust from scrambler inspiration kit. I had a feeling that something was wrong except from the heat on my right leg and removal of passengers foot pegs. Today i went to the dyno and dynoed the bike. Result is that the bike is underpowered and without that torquey think at low rpm. It totaled at 50,97 HP which is 2 horses less than the original according cycle worlds dyno. Bike is also reflashed from Triumph because as they say it is racing "ha ha" of road exhaust and needs to reprogram ecu (probably to underpowered it). After paying almost 1300 euros for the exhaust i will not accept a compromise of loosing money and comfort and not gaining at least something more at responsiveness and power.
Probably i will sell the exhaust which is brand new to someone that want to spend some time how to upgrade this bike.
 

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mpak - You are apparently confused about how a dyno works. Dyno results are subject to many variables, including air temperature, atmospheric pressure, physical differences between engines, dyno operating procedures, etc., just to name a few. The same bike could easily show a 2 HP difference between two runs on the same dyno; comparing runs of different bikes on different dynos is meaningless. If you had wanted to know the effect of changing your exhaust system, you should have made a dyno run with the stock exhaust, installed the new one, and dyno'ed the bike again, preferably on the same day. The only real value of a dyno is to make such before and after comparisons on the same dyno and bike.

With that said, an engine is basically an air pump. As Haggis noted, removing restriction from the exhaust (i.e. pump output) side will only increase power if the engine was being prevented from making maximum power due to exhaust restriction. On some specific bikes, that is undoubtedly the case, due to differences in their individual engines (e.g. tolerance stacking, etc.). In other words, if you dyno'ed a lot of bikes with and without a given exhaust, some would show a significant increase in power (e.g. typically 4 - 6 HP peak) others would not. Reducing the intake restriction as Haggis suggested may increase the amount of power your engine makes, but only if it is capable of using more air. Other modifications may be required for it to do so (e.g. porting the head, installing higher performance cams, etc.).

Decades ago, factory exhausts were typically built as inexpensively as possible and replacing them with a more carefully designed and built exhaust system would almost always produce measurable power improvements. However, modern OEM exhausts are very well designed and built and such gains are no longer assured. Moreover, the loss of some low-end torque is a natural consequence of reducing exhaust restriction (i.e. it "proves" the new exhaust is functioning as intended). These are all well known facts that you could have found by reading this or almost any other performance forum. Doing so might have saved you 1300 euros or you could just wait for a clear, cold day and dyno your bike again.
 

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I would not put to much into that cycle world dyno you may have picked up hp with your changes but you wont ever know because you never put it on the dyno stock so you could compare. all most 51 hp maybe be good for what you have.
 

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How does it sound now? Some change exhaust to improve the sound.

I put off road exhausts on my Thunderbird, for me it was to improve the sound, I was not so worried about increasing HP.
 

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Discussion Starter · #10 ·
Sound is great , but it lost low rpm torque so you have to rev it more so it's more noise .
 

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Very common for aftermarket exhausts to lose low end torque at the expense of more power up top. Any differences in the power at higher rpms?
 

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Dear mpak, be careful that feelings alone can be very deceptive. Riding your bike, maybe in a week or two you may change your mind. If you are so convinced about your sensations, having already spent eur 1300, I would switch to original exhaust again and dyno it. Make some acceleration tests and top speed tests (if possible) for both exhausts and record your findings.

IMHO changing exhaust is more of a sound and look mod, not about strong performance gains. Perhaps your expectations were too high?
 

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Discussion Starter · #13 ·
Ok the facts. Open muffler, catalyst off,Ecu reflashed for better performance. The result is minus 1 hp from a total normal bike. Why I am the only one that finds that odd? i cannot agree that the bike maybe produce let's say 49hp normal and is on gain. X engine was 67hp , cycle worlds dyno 51hp declared 55hp , mine was the black sheep ?
 

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You have no accurate control to compare the current dump run to. As others have said, put it in the dump stock and mod and then you will know the effect. Comparing the dump results to a magazine result on a sidemen dyno and different testing circumstances isn't sound science.

I'm not saying that you're wrong but you don't really know how much it changed!


Sent from my iPhone using Tapatalk
 

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Ok the facts. Open muffler, catalyst off,Ecu reflashed for better performance. The result is minus 1 hp from a total normal bike. Why I am the only one that finds that odd? i cannot agree that the bike maybe produce let's say 49hp normal and is on gain. X engine was 67hp , cycle worlds dyno 51hp declared 55hp , mine was the black sheep ?
Minus 1hp from CLAIMED horsepower under ideal conditions at sea-level in the UK.
 

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Minus 1hp from CLAIMED horsepower under ideal conditions at sea-level in the UK.
I think that is the problem, it's a well known fact that UK air is higher octane.

I have 2 tyre pressure gauges and if I measure the pressure with each of them I get a different readings, don't understand why, its the same tyre it's measuring.
 

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Minus 1hp from CLAIMED horsepower under ideal conditions at sea-level in the UK.
clamed hp is crank hp not rear wheel hp you loose about 13 hp to the rear wheel.truth be known the st stock does not make that great of hp ( less then the older bikes stock) the older bikes stock made about 50 hp on the rear wheel the st makes less.that dyno in that mag is just plan bs.
 

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You've made a bunch of changes. Why are you assuming that the exhaust is sub-par? I'd wonder about the tune, too. Maybe there is no problem at all; a before dyno is (or was) the only way to know.
 

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Discussion Starter · #19 ·
My next steps are , an open filter and a reflash of the Ecu from a programmer. Then dyno and we will see
 

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a reflash of the Ecu from a programmer.
Are there suitable tune maps for anything more complicated than an official exhaust change? Be careful, we don't yet know if these late ECU's can be re-programmed by anything other than the official Triumph tools and officially available tunes certainly won't contemplate air filter or airbox mods.
 
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